Storage for a virtual environment, i.e., a so-called virtual storage apparatus has been present as a storage system capable of realizing a memory device having free volume configuration and storage capacity without being restricted by volume configuration and storage capacity of a physical memory device. The virtual storage apparatus has within the apparatus a real storage apparatus controlling access to a physical memory device and creates a virtual volume with a processor managing the real storage apparatus.
The virtual storage apparatus performs data access through wide striping, for example. Wide striping is a technique of distributing data access of one volume to multiple logical unit numbers (LUNs) such that access is performed in units called strips having a fixed length.
As the memory capacity required for the virtual storage apparatus increases, the entire memory area of the virtual storage apparatus may be expanded. A method of expanding the entire memory area of the virtual storage apparatus may be, for example, addition of an expansion set that is a set including a processor that manages a real storage apparatus and the real storage apparatus.
To enable a fallback at the occurrence of a failure such as a failure of a processor in a virtual storage apparatus, the processors and the real storage apparatuses in the virtual storage apparatus may be connected in full mesh via a switch. If a switch is added in association with addition of an expansion set to the virtual storage apparatus, the switches are cascade-connected to realize full mesh connection of the processors and the real storage apparatuses.
Related technologies include, for example, a technique of forming groups of multiple disks to assign respective memory areas from multiple groups to virtual volumes and rearranging the memory areas of the groups used by the virtual volumes based on an external operation. Another related technology is a storage system having multiple switch ports and configured to include a switch such that if a data frame is input to a certain switch port, the switch outputs the data frame to a switch port leading to a connection port having the address specified by the data frame. For examples of such technologies, refer to Japanese Laid-Open Patent Publication Nos. 2008-234158 and 2003-330762.
Nonetheless, the conventional techniques have a problem in that, at the time of access of data distributed and arranged in multiple real storage apparatuses in a system, communication traffic increases on a route of cascade connection between switches, resulting in deterioration in access performance to the real storage apparatuses.